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nanotimes News in Brief

11-02/03 :: February / March 2011

Data Storage // Mini Disks for Data Storage – Slanted Edges Favor Tiny Magnetic Vortices

S

lanted exterior edges on tiny magnetic disks could lead to a breakthrough in data processing.

“By this, structures are created which were impossi- ble in the past;” explains Jeffrey McCord, a materials researcher at the Helmholtz-Zentrum Dresden-Ros- sendorf, Germany. The doctoral candidate Norbert Martin produced the slanted edges in a lab experi- ment; thus, creating magnetic vortices with a diame- ter of only one third of a thousandth of a millimeter. This could help to store larger amounts of data on increasingly smaller surfaces with as little energy as possible.

Tiny magnets organize themselves in vortices in the researchers’ mini disks. The individual magnets can twist either in a clockwise or a counterclockwise direction in the disk. These two different states can be used in data processing just like switching the electricity “on” and “off” in conventional computers. In contrast to conventional memory storage systems, these magnetic vortices can be switched by the elec- trons’ intrinsic spin and with far less power consump- tion.

In the exterior section of a vortex the magnetic particles align nearly parallel to one another while the space in the disk’s center is insufficient for such a parallel arrangement. Therefore, the elementary magnets in the center of a vortex twist away from the

surface of the disk in order to gain space and thus, orient themselves once again next to one another without consuming much energy.

The formation of a vortex only works smoothly if the individual magnetic disks maintain some distance to one another or are relatively big. In order to achieve a high data storage density for compact and efficient devices, manufacturers and users ask for the smallest possible data processing units, which in turn also feature small magnetic vortices and require a closely packed structure. Then, however, the tiny magnets in each disk „feel“ their neighbors in the adjacent disks and start to interact. This interaction, though, is a poor prerequisite for memory storage systems.

Therefore Norbert Martin and Jeffrey McCord elimi- nated the cylindrical shape of the small magnetic disks and instead prepared them with slanted edges. The tiny magnets at the edges are thus forced in the direction of the slant. This orientation creates in turn a magnetic field perpendicular to the disk surface, which then is in the preferred direction of the slant.

This requires a lot less energy than the symmetric ori- entation of this magnetic field for the disks with verti- cal outer edges. Accordingly, magnetic vortices form more easily with slanted edges. To create these vor- tices, Norbert Martin places tiny glass spheres with

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